If you like running, walking, riding etc, then
RUNKEEPER is a good one to track your progress. Funny though i use it less the older i get
Also there was a good article in the free March 2013 issue of ARB 4x4ACTION about iphone photography apps. If you are like me and couldn't be bothered carrying your camera around now you have an iphone then this is a good article. Two of the apps i will be trying from the artcile are
CAMERA AWESOME (free) and
SLOWSHUTTER ($0.99).
If you are a coffee lover
BEANHUNTER (free) can be handy when you are in a new area and need to find a good coffee (i.e. not Macca's).
Also another vote for
wikicamps, we used it heaps on our Vic/Tassie holiday last year.